Holshof G., Galama P.G. and Zom R.L.G.
Wageningen UR Livestock Research, P.O. Box 338, 6700 AH Wageningen, the Netherlands;
gertjan.holshof@wur.nl
Abstract
Dairy herds in the Netherlands will increase in size the coming years, due to the abolishment of the European milk quota. As the available grazing area per dairy farm will not increase, exploring new ways of grazing with a high stocking rate has priority. At Dairy Campus – a Dutch experimental farm – three grazing systems with 6 cows per ha were tested: strip grazing (SG), one-day rotational grazing with a fixed paddock area and a fixed growing period of 23 days (DRG) and rotational continuous grazing (RCG).
The daily grazing time was restricted. The grassland and animal performance of the three systems were compared. The fresh grass intake was 8.3 kg dry matter (DM) cow-1 day-1 for DRG and 6.3 kg for SG and RCG. The milk production of the three systems (25.4 kg milk) was not significantly different. All three systems are suitable for grazing with a high stocking rate, but the highest fresh grass intake was measured at the DRG system.
Keywords: grass intake, grazing, grazing system, large herds, supplementary feeding, stocking rate
Introduction
Grazing provides many economic opportunities, e.g. less contract work for making silage and for applying manure (Reijs et al., 2013). Nevertheless more farmers tend to keep their dairy cows housed all year round to maintain milk production at a high level. Farmers consider it difficult to manage grazing due to highly variable weather conditions. Furthermore, they think grazing causes high losses and is time consuming.
Recently the average herd size has increased, resulting in higher stocking rates on the grazing platform.
These aspects, combined with milking with an automatic milking system (AMS), are causes for a decline in grazing (Van den Pol-Van Dasselaar et al., 2015). To address these challenges, easy manageable grazing systems for farms with high stocking rates have been developed at the research farm ‘Dairy Campus’ in Leeuwarden, the Netherlands. The aim of this study was to study the grass and animal performance of three possible grazing systems with high stocking densities. In two separate experiments grass intake was measured by the alkane technique and in relation to cow movement (sensor data, Timmer et al., 2016).
Materials and methods
In 2015, a grazing experiment was carried out at research farm ‘Dairy Campus’, Leeuwarden, the Netherlands. In this experiment three grazing systems were compared: strip grazing system (SG), a
‘rotational’ continuous grazing system (RCG) and a daily rotational 24 paddock grazing system (DRG).
Each grazing system was executed with 20 cows, on 3.33 ha resulting in a stocking rate of 6 cows ha-1. At night the cows were fed silage and concentrates. For DRG, the grass allowance depended on the grass production in 23 days on the fixed paddock. If there was enough grass, cows also had access during the night time. On the strip grazing and continuous grazing systems, cows had only access to the grass during day time between two milkings. Based on the high stocking rate it was expected that none of the three systems would produce enough grass for full time grazing during the whole season, so supplementary feed was needed. All cows received a flat rate of 5 kg concentrates per cow per day. The amount of supplementary feed as a total mixture of grass silage (30%) and maize silage (70% on dry matter (DM) base) depended on the grass growth and was fed after the evening milking. The SG system was aimed at a daily grass allowance of 8 kg DM per cow. At this allowance level it should be possible to mow for
silage to obtain fresh aftermath. If the grass growth decreased, less fresh grass and more supplementary feed was provided. The RCG system had six blocks of 0.55 ha. Cows got access to a new block every day and rotated on five blocks. The sixth block was used for silage to obtain aftermath. In the DRG system, paddocks were only used for silage if the grass allowance was too high. The cows received a fresh paddock every day and the maximum rotation length was 23 days. Cows had to graze the available amount of grass in a paddock in 24 hours or less. If the grass allowance was too low for a 24 hour grazing period, cows got supplementary feed and were kept inside after the evening milking or from 22.00 hours onwards. The body condition score was measured and animal weights were recorded once every month. Differences in milk production per cow, amount of supplementary feed and gross grass production were compared between the three systems. Feed intake and milk production were statistically analysed with ANOVA.
The grazing system was used as fixed factor.
Results and discussion
Fresh grass intake (FGI) (kg DM cow-1 day-1) was calculated from the net energy (NE) requirements for milk production, maintenance and growth (NE-req, MJ cow-1day-1) the NE intake from supplemental feeding (NE-suppl, MJ cow-1 day-1) and an estimated NE content of the grazed herbage (NE-grass; MJ kg DM) as FGI: (NE-req-NE-suppl)/NE-grass. The results of the three grazing systems are presented in Table 1
The DRG group had the highest fresh grass intake due to the possibility of a day and night grazing period in May. Therefore the supplementary feed intake was the lowest for this group. For the other two systems day and night grazing was not possible. The SG system needed aftermath and in the RCG system a certain grass stock was necessary to obtain enough daily grass growth. For all three systems animal condition and weight declined in the first three months of the experiment and increased after July. The herd had a calving period from December to April. There were no significant differences in condition or weight between the three grazing systems. The fat and protein corrected milk production is presented in Figure 1. The fat percentage of the DRG was slightly lower with 4.22 to 4.40% for both other groups, but not significantly different. There was no significant difference in milk production.
The rotational continuous grazing system was the most difficult to manage. There should be a balance between daily grass growth and daily grass intake, but in practice a large amount of grass was refused. It was difficult to find the optimal number of grazing hours. In this system cows were kept inside for a few weeks in July to clean up the paddocks and to get a fresh aftermath. The 24 paddock system (DRG) was easiest to manage. The grass allowance was measured every day and the grazing time was determined.
The DRG system provided the highest grass intake. If the farmer is able to measure the amount of grass daily, the RCG system is easy manageable. All three systems have potential for grazing with large herds
Table 1. Grassland data and feed intake of three grazing systems for high stocking rates.
System (data from 2015) Daily rotational Strip grazing Continuous grazing
Supplementary feeding (kg DM cow-1 day-1) 5.9 8.3 8.1
Daily calculated fresh grass intake (kg DM cow-1 d-1 8.3 6.3 6.6
Number of grazing days 183 183 183
N fertilisation (kg N ha-1) 234 244 171
Net yield grass silage (ton DM ha-1 year-1)a 1.20 1.45 1.33
Total grass intake per system (ton DM ha-1 year-1) 9.2 7.0 7.3
Net yield grazing platform total (ton DM ha-1 year-1) 10.41 8.40 8.67
a Net grass silage is the amount of DM after field and conservation losses.
on a small grazing platform. Personal preference of the farmer will be an important reason for choosing a certain grazing system.
Conclusions
All three grazing systems, strip grazing, one-day rotational grazing with a fixed paddock area and rotational continuous grazing are suitable for grazing large herds on a relatively small grazing platform.
There was no significant difference in milk production, cow weight and animal condition between the three tested systems.
References
Reijs J.W., Daatselaar C.H.G., Helming J.F.M., Jager J. and Beldman, A.C.G. (2013) Grazing dairy cows in North-West Europe;
Economic farm performance and future developments with emphasis on the Dutch situation, Report 2013-001, LEI Wageningen UR, The Hague, 124 pp.
Van den Pol-Van Dasselaar A., de Vliegher A., Hennessy D., Isselstein J. and Peyraud J.L. (2015) The future of grazing. Proceedings Third Meeting of the EGF Working Group ‘Grazing’. Wageningen, Livestock Research report 906, 38 pp.
B. Timmer, R.L.G. Zom, G. Holshof, W. Pellikaan, C.G. and Van Reenen (2016) The application of behaviour sensors and sward height measurement to support grazing management. The Multiple Roles of Grassland in the European Bioeconomy. Grassland science in Europe 21, (this volume).
10.0 15.0 20.0 25.0 30.0 35.0
27-4 16-6 5-8 24-9 13-11
kg FPCM cow-1 day-1
Date
DRG SG RCG
Figure 1. Fat and protein corrected milk production (FPCM) (kg cow-1 day-1) for the grazing systems: strip grazing system (SG), a ‘rotational’
continues grazing system (RCG) and a daily rotational 24 paddock grazing system (DRG).